Primary Production from Oxide Ores

Oxide ores are generally treated by hydrometallurgical processes. After concentration they are leached with sulfuric acid. The copper-rich solutions are then treated by solvent extraction (SX) and copper is finally obtained by an electrolytic process (EW). The combined process is designated SX/EW. 

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Iron (III) oxide exists in mineral form as hematite. It is 70% iron and is the primary source of iron ore in the world. About 90% of the iron mined in the United States is hematite. World production of this ore is more than 1 billion tons. Magnetite and taconite are two other primary iron oxide minerals used as iron ore. The name hematite comes from the blood-red color of powdered hematite. The Greek word hematite means blood-like. Some ancients held the belief that hematite was formed in areas where batdes were fought and blood was spilled into the earth. Large deposits of hematite have been identified on Mars. 

Silver occurs both as native ore and in combination with various silver sullide minerals. Native silvct is predominantly a product of primary deposition from hydrothermal solutions. Minor occurrences are products of oxidation of silver sullide minerals with which the native ore is seenndarily associated, Sec also Silver. 

Only about one-fourth of the elements occur naturally in the free state. Most are found in a combined state. The process of obtaining a metal from its ore is called metallurgy. Since the metals in ores are found in the form of cations, the chemistry of metallurgy always involves reduction of the ions to the elemental metal (with an oxidation state of zero). A variety of reducing agents can be used, but carbon is the usual choice because of its wide availability and relatively low cost. For example, carbon is the primary reducing agent in the production of steel. Carbon can also be used to produce tin and lead from their oxides ... 

Uranium U(VI) minerals are most often products of the oxidation and weathering of nearby primary U(IV) ore minerals such as uraninite [U02(c)I and coffinite [USi04(c)l (cf. Pearcy et al. 1994). They also form by evaporative concentration of dissolved U(VI), particulary under arid conditions. Schoepite (/J-UOj 2H2O) is fairly soluble and, therefore, is a rare mineral, whereas carnotite K2(U02)2(V04)2j and tyuyamunite (Ca(U02)2(V04)2j, which have lower solubilities (particularly above pH 5) are the chief oxidized ore minerals of uranium. The plots in Figs. 13.5 and 13.6 indicate that uranyl minerals are least soluble in I0W-CO2 waters, and, therefore, are most likely to precipitate from such waters. This is con.sistent with the occurrence of carnotite and tyuyamunite in oxidized arid environments with poor. soil development (Chap. 7), such as in the calcrete deposits in Western Australia (cf. Mann 1974 Dall Aglio et al. 1974), and in the sandstone-hosted uranium deposits of the arid southwestern United States (cf. Hostetler and Carrels 1962 Nash et al. 1981). The... 

Over 95% of failed lead—acid batteries are recycled in these pools, yielding secondary lead which is re-used for the manufacture of new lead—acid batteries. The secondary lead is purified to a degree, allowing its utilization in the production of leady oxide and lead alloys. A certain amount of primary lead extracted from lead ores is also added to the lead pool and used in the manufacture of leady oxide. Thanks to the high percentage of recycled secondary lead and the simple technology of manufacture, the lead—acid battery is the cheapest chemical power source available. 

The manufacture of copper metal from ores is called the primary production. Ores worked may be of oxide or sulfide type. Only 9% of exploitable copper resources worldwide consist of oxide ores while 90% are sulfide ores. When copper metal is manufactured from scrap it is a secondary production. 

Historically, slags have been an important by-product of the smelting of ores to produce metals. They serve the primary purpose of dissolving all of the extraneous rock into one homogeneous liquid from which the heavier metal reduced to its elemental state can separate by simple gravity segregation. They can also serve to absorb certain metal oxides while allowing another to be reduced to the elemental state. In some... 

By-product processing is also largely by crushing and flotation, but the flotation processes are more specialised because of the variety of ores involved and the need to separate the small molybdenum content from the major proportion of copper or other primary metals. Because the product is mainly used in steelmaking, oxidation to molybdic oxide is acceptable, and an intermediate roasting may also be used. 

World mine production of copper is currently in the range of 13-14 Mt, about a third of which is from Chile. Other large producers are the United States, followed closely by Indonesia and Australia. The most important ore mineral is chalcopyrite [CuFeS2], and also significant are bornite [CusFeSJ and chalcocite [CU2S]. The first two are primary minerals, whereas chalcocite forms principally by their weathering and subsequent reprecipitation of the solubilized copper as enriched blankets of chalcocite ore beneath the oxidation zone. 

Litharge and the other lead oxides that are used in the production of glasses and ceramics are obtained primarily through the oxidation of refined (purified) metallic lead. Because metallic lead does not occur naturally in large quantities, it must be extracted from either primary sources (mineral ores) or secondary sources (recycled materials such as lead-acid batteries and cathode ray tubes). The processing required to refine metallic lead can be broken down into three major steps, as seen in Fig. 3 ... 

Especially important for proper operation of the battery are the impurities contained in the metal used for leady oxide manufacture. Lead for the battery industry is derived from ores mined in different parts of the world (primary lead) or is obtained by recycling of used up batteries that have reached their end of fife (secondary lead). The recycling process is very often performed at the battery manufacturers facilities. Purity standards have been adopted for the lead to be used for leady oxide production. These standards specify different maximum allowable amounts of impurities for flooded and valve-regulated lead-acid battery applications. Table 5.2 presents typical purity specifications for lead for making leady oxide for flooded batteries. 

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